Pneumatic control system with pneumatic logic elements for signal processing

ABSTRACT

In a pneumatic control system having pneumatic logic elements for signal processing to perform a control function, the elements are divided in two groups. The first group require an energy supply to change their states but do not require the energy supply to maintain a stable state. The second group require energy both to change state and to maintain a set state. The second group are connected directly to a pneumatic energy source while the first group are connected through an on-off control means so that energy is applied thereto during signal processing and is removed in a stable state of the system so as to avoid unnecessary energy consumption in the first group. The control means may be actuated to allow energy supply to the first group by a device responsive to incoming signals for processing by the system.

United States Patent Boros et al.

PNEUMATIC CONTROL SYSTEM WITH PNEUMATIC LOGIC ELEMENTS FOR SIGNAL PROCESSING Inventors: Andor Boros; Laszlo I-Ielm; Zsolt Marton; Attila Szucs, all of Budapest, Hungary Magyar Tudomanyos Akademia Automatizalasi Kutato Intezet, Budapest, Hungary Filed: Nov. 8, 1971 Appl. No.: 196,345

Assignee:

[56] References Cited UNITED STATES PATENTS 3,201,041 8/1965 Welsh 137/81.5 X 3,370,790 2/1968 Schonfeld et a1. 235/201 3,461,777 8/1969 Spencer 137/815 X 3,531,985 10/1970 Martin 137/815 X 3,603,334 9/1971 Davies et al. l37/81.5 3,687,150 8/1972 l-loglund 137/8l.5 3,493,173 2/1970 Monge et al 137/8l.5 X

3,420,254 l/l969 Machmer -137/81.5 3,427,962 2/1969 Giannuzzi et al... l37/8l.5 X 3,463,176 8/1969 Lazar 137/8l.5 X 3,481,351 12/1969 Reilly et a1... 137/81.5 3,530,884 9/1970 Kutz 137/81.5 X 3,565,114 2/1971 Rousseau 137/8l.5 X 3,626,473 12/1971 Posingies l37/8l.5

3,642,016 2/1972 Budzich 137/8l.5 3,646,963 3/1972 Klee 137/8l.$ X 3,656,510 4/1972 Kinner 137/8l.5 X

Primary ExaminerSamuel Scott Att0rneylrvin S. Thompson et a1.

[5 7] ABSTRACT In a pneumatic control system having pneumatic logic elements for signal processing to perform a control function, the elements are divided in two groups. The first group require an energy supply to change their states but do not require the energy supply to maintain a stable state. The second group require energy both to change state and to maintain a set state. The second group are connected directly to a pneumatic energy source while the first group are connected through an on-off control means so that energy is applied thereto during signal processing and is removed in a stable state of the system so as to avoid unnecessary energy consumption in the first group. The control means may be actuated to allow energy supply to the first group by a device responsive to incoming signals for processing by the system.

2 Claims, 5 Drawing Figures Patented Nov. 13, 1973 4 Sheets-Sheet 1,

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Fig.2

Patented Nov. 13,1973 I 3,771,569

4 Sheets-Sheet 2 R0 R R1 ('4 /I Fig.3

Patented Noy'. 13, 1973 3,771,569

4 Sheets-Sheet 5 Fig.4

Patented Nov. 13, 1973 4 Sheets-Sheet 4 Fig.5

PNEUMATIC CONTROL SYSTEM WITH PNEUMATIC LOGIC ELEMENTS FOR SIGNAL PROCESSING This invention relates to a pneumatic control system and is concerned with the supply of supply energy to pneumatic logic elements, such supply energy being required'at least when a change of state of the elements is to be effected.

The term pneumatic as used herein is used to embrace logic elements operating with both gases and liquids as are known in the art of what is commonly termed fluidics or fluidic logic. The description given hereinafter will particularly relate to gas-operated systems and more specifically those systems using air as the .operating medium.

It is generally desirable to reduce the requirements placed on a pressurised supply of air used as an energy source for a pneumatic control system. Systems with very low operating frequencies are found relatively often among pneumatic systems. In such systems the period spent in a stable state of the system is generally substantially greater than that spent in a transitional state (i.e. change of state). This is particularly likely with systems consisting of fluid type elements without moving components and also showing a continued energy consumption in the stable state.

The use of logic elements which only require supply energy in the transitional state enable this energy consumption to be reduced so that in the ideal case, the leakage loss of the logical elements would be zero. It should be noted that the logic elements which only consume supply energy in the transitional state are, at the present state of the art, necessarily units with moving components. In accordance with previous practice however, fluid elements without moving components have been so arranged that there is an energy loss associated with them in the stable state also. The supply energy can thus beregarded as expended in two parts. A useful energy enabling a change of state to be effected and a loss energy during the stable state when theoretrically no supply energy is required to maintain that state.

The greater the proportion of loss, associated with the useful energy consumption of an element, the more the need to devise a procedure by which the high energy consumption of control systems heretofore built up from elements without moving components can be reduced to an economically acceptable level.

The invention enables us to provide a pneumatic control system in which the disadvantages of the prior practices set out above are at least mitigiated. In its broadest aspect the invention provides a pneumatic control system comprising .a plurality of pneumatic logic elements at least a group of which are of a kind requiring no supply energy to maintain them in a stable state once having been set into said stable state, first means coupled to the elements of said group and connectable to a source of pneumatic energy, said first means being actuable to a first condition allowing the application of pneumatic energy to the element of said group as supply energy therefor whereby changes in the states of the elements of said group may be effected, and to a second condition preventing the application of pneumatic energy to the elements of said group as supply energy therefor, and second means operable to set said first means into said first or second condition.

considered as composed of subsystems which require supply energy in the stable state and/or in the transitional state. The duration of the stable operating state in pneumatic logical systems is generally longer than that of the transitional state, so that in the majority of cases it is most advantageous if all or part of the control input supply energy of the logic system is only switched on for the duration of the transitional state and the energy supply of the system in the stable operating state ceases in whole or in part.

Although the question of energy consumption discussed above is always taken into account in the development and construction of pneumaticsystems, as far as we are aware it has always been approached exclusively from the requirements of the individual logic elements. A relatively low energy consumption has always been one of the decisive points in the construction of a logical element. The arrangement of the individual elements has, however, determined the energy consumption of the system in practice.

We have had regard to a pneumatic control system considered as a whole and have set out to provide a new type of switching technique by which the energy consumption of a logical pneumatic control system is reduced enabling a more economic use of energy to be achieved. Accordingly, we now propose more specifically an arrangement for the economic energy supply of a pneumatic control system having at least one input connected to receive signals for processing by the system and at least one output which can be connected to a controlled process, or to an external control such as a manually-actuated control or an automatic program. The system for processing the signals comprises pneumatic logic elements interconnected to provide the desired control function at the output. The pneumatic control system is divided into a first subsystem of elements which does not require supply energy to be maintained after having been set into a stable state and a second subsystem which does require the maintenance of supply energy. Each subsystem is connected separately to at least one energy source, with an energy control means provided between the first subsystem and the energy source, the energy control means having an actuating input to which the output of a signal state sensing device is connected. The input of the sensing device is connected to the aforementioned input of the pneumatic control system and is operable to put the energy control means into a condition allowing energy supply to the first subsystem when a signal input is received which may require changes of state among the FIG. 3 shows in block diagram form one embodiment of a pneumatic control system in accordance with the invention;

FIG. 4 shows in block diagram form another pneumatic control system in accordance with the invention;

FIG. 5 is the block diagram of one possible arrangement of the second subsystem R within the system of FIG. 4 requiring a continuous supply of supply energy at two levels. Like reference numbers indicate like parts throughout the drawings.

FIG. 1 illustrates the sequence of changes of state of a pneumatic control system composed of logic elements. The value 1 represents the transitional state on the ordinate axis Y, while the stable state is represented by the value 0. The abscissa axis represents time. The durations of the transitional state are indicated by m and the average value of the repetition durations is indicated by 1-. The duration of the transitional state is constituted by the period required for the new balanced state to be reliably achieved after a modification of the input to control system causing a change of state of one or more elements therein. The average frequency of the system is equal to the reciprocal value of the average repetition frequency 1 i.e.

The energy consumption of the system during the period m is the useful consumption, while the consumption during the period 1- m is the loss consumption. When speaking of the control system in what follows, it is to be understood that reference is being made to those logic elements which participate exclusively in the processing of information. Excluded are the various elements for supplying or removing the information, the power elements and the elements for executing and indicating.

If a general pneumatic control system R, such as is shown diagrammatically in FIG. 2, is examined with regard to energy requirements, the following can be ascertained:

The pneumatic control system R can be divided into a first subsystem R and a second subsystem R The first subsystem R stores information without supply energy, while the second subsystem R requires supply energy for storage purposes. The elements can be grouped into the two subsystems on the basis of this difference.

A pneumatic system R can generally contain storage elements M and counter elements T, so that an element group is present built up from the two elements mentioned, i.e. from sequential elements. This group forms a first MT element group. The first element group MT can have the following sub-groups:

a first MT sub-group, in which the elements also require full energy supply in their stable state or states; a second sub-group MT, in which the elements require a moderate energy supply in their stable state or states; and a third sub-group MT, characterised by the fact that the elements require no supply energy in their stable state or states.

Where sequential elements are not used at all in the pneumatic system R, the subsystem R, is the actual pneumatic control system.

FIG. 2 shows the implementation of the prior techniques in the operation of a pneumatic control system R. The first subsystem R and the second subsystem R are both connected continuously to an energy source P, for their power supplies, although such energy is not necessary for the first subsystem R in the stable state.

On implementing a control system in accordance with the invention, those properties of the pneumatic control system connected with running periods of the signals progressing in the system must be taken into account accordingly. 7

The teachings of the present invention can be appreciated from FIG. 3 which shows oneembodiment of a control system in accordance with the invention. The pneumatic control system R consists of the subsystems R and R as first and second subsystems. The first subsystem R is connected to the output of a control means S such as an on-off valve disposed in the energy supply line from the source P, to the control inputs of the logic elements in subsystem R the elements not being individually shown. Thus the energy control means S is actuable to a condition in which it connects the energy source P, with the first subsystem R and allows application of pressure to the elements therein. The control 1 means S has an input which is connected to the output of an actuating device D, which can consist, for example, of a manually actuated or automatic signal transmitter. The automatic actuation can be effected by an external program transmitter or by an input of the pneumatic control system R which can be derived from the controlled process. The device D shown has an input connectable through switch K to the signal input to the control system R. The device D normally maintains the control means S in a condition preventing the application of energy to subsystem R from source P,. When the switch K connects the input of device D to the input of control system R, the device D acts to sense a change of state of the signal input and is responsive to such a change to-put the control means S into the open condition allowing pressure to be applied to the supply ports of elements of subsystem R so that they can process the incoming signals by changing their states as required. These signals are also processed by subsystem R to which pressure is continuously applied from source P,.

The embodiment shown in FIG. 4 differs from that of FIG. 3 in that the first subsystem R contains a thirdtype of sub-group MT,, and the second subsystem R contains a first type of sub-group MT and a second type of sub-group MT both these latter groups requiring a higher or lower level respectively of supply energy to maintain them in their stable states.

The output of the signal-state sensing device D is connected to the actuating input of the control means S while the actuating input of the device D is connected to the input of the pneumatic control system R. The second subsystem R is connected directly to the energy source-P, as is the supply input of the device D.

FIG. 5 shows how the subsystem R of FIG. 4 can be arranged to further economise on the supply-of energy to elements in the sub-group MT, which cannot store when the energy supply is switched off but do not require full supply energy to maintain them in the stable state. In FIG. 5 the sub-group MT, retains the stored information by the fact that a substantial part of the supply energy in the stable state is switched off since more supply energy is required for them to acquire information (i.e. change state) than is required to pass the information on in the stable state.

To this end there is provided a high pressure energy source P and a low pressure energy source P The high pressure energy source P can be switched off by means of pneumatic switch C during the stable state. During the transitional state, the high pressure source P is switched on by the closing of switch C. In order to prevent the high pressure energy source P from feeding back into the low pressure source P a nonreturn valve V acting like an electronic diode is provided in the line between the low pressure energy source P and the sub-group of elements MT We claim:

l. A pneumatic control system comprising a plurality of pneumatic logic elements at least a group of which are of a kind requiring no supply energy to maintain them in a stable state once having been set into said stable state, an input for receiving signals to be processed by the control system, first means coupled to the elements of said group and connectable to a continuous source of penumatic energy, said first means being actuable to a first condition allowing the application of said pneumatic energy to the elements of said group as supply energy therefor whereby changes in the states of the elements of said group may be effected, and to a second condition preventing the application of pneumatic energy to the elements of said group as supply energy therefor, and second means operable to set said first means into said first or second condition, said second means being operable to normally maintain said first means in said second condition, and means for connecting said second means to said control system input to sense the receipt of a signal thereat and to put said first means into said first condition to enable signal processing to be effected in the control system.

2. A pneumatic control system comprising a plurality of pneumatic logic elements at least a group of which are of a kind requiring no supply energy to maintain them in a stable state once having been set into said stable state, first means coupled to the elements of said group and connectable to a continuous source of pneumatic energy, said first means being actuable to a first condition allowing the application of said pneumatic energy to the elements of said group as supply energy therefor whereby changes in the states of the elements of said group may be effected, and to a second condition preventing the application of pneumatic energy to the elements of said group as supply energy therefor, second means operable to set said first means into said first or second condition, at least a further set of pneumatic logic elements of a kind requiring a higher level of supply energy to change the states thereof than that required to maintain them in a stable state, a first source of lowerlevel pneumatic energy coupled to the elements of said set through a non-return valve to maintaim them in a stable state after having been set therein, and a second source of higher level pneumatic energy coupled to the elements of said set through a pneumatic switch operable to allow said higher level energy to be applied to the elements of said set when a change in the stable states thereof is to be effected. 

1. A pneumatic control system comprising a plurality of pneumatic logic elements at least a group of which are of a kind requiring no supply energy to maintain them in a stable state once having been set into said stable state, an input for receiving signals to be processed by the control system, first means coupled to the elements of said group and connectable to a continuous source of penumatic energy, said first means being actuable to a first condition allowing the application of said pneumatic energy to the elements of said group as supply energy therefor whereby changes in the states of the elements of said group may be effected, and to a second condition preventing the application of pneumatic energy to the elements of said group as supply energy therefor, and second means operable to set said first means into said first or second condition, said second means being operable to normally maintain said first means in said second condition, and means for connecting said second means to said control system input to sense the receipt of a signal thereat and to put said first means into said first condition to enable signal processing to be effected in the control system.
 2. A pneumatic control system comprising a plurality of pneumatic logic elements at least a group of which are of a kind requiring no supply energy to maintain them in a stable state once having been set into said stable state, first means coupled to the elements of said group and connectable to a continuous source of pneumatic energy, said first means being actuable to a first condition allowing the application of said pneumatic energy to the elements of said group as supply energy therefor whereby changes in the states of the elements of said group may be effected, and to a second condition preventing the application of pneumatic energy to the elements of said group as supply energy therefor, second means operable to set said first means into said first or second condition, at least a further set of pneumatic logic elements of a kind requiring a higher level of supply energy to change the states thereof than that required to maintain them in a stable state, a first source of lower level pneumatic energy coupled to the elements of said set through a non-return valve to maintaim them in a stable state after having been set therein, and a second source of higher level pneumatic energy coupled to the elements of said set through a pneumatic switch operable to allow said higher level energy to be applied to the elements of said set when a change in the stable states thereof is to be effected. 